Millennials are spending more money on stocks than they would on cups of coffee or items on Amazon, the co-founder of a stock trading app said in a new interview.

Vlad Tenev, who co-founded the app Robinhood and now works as its CEO, told Business Insider the company's customers tend to use discretionary money instead of cash they've stashed away in a savings account.

"You have these people that maybe are buying 50 different stocks but one or two shares of each and they're creating these diversified portfolios using small amounts of money. That type of transaction would have cost thousands of dollars in the past — people just wouldn't have done it," Tenev said.

He added that the money people are putting into their trading "is money that would have been spent on coffee or on Amazon or just discretionary stuff."

The stock market has performed well under President Donald Trump despite the claims of Russian collusion that have echoed for months.